Making flan in a 22in. clear glass Arc Intn'l. (Corning/Pyrex made in France) mold I must first pour hot melted sugar in the mold. Will this crack the mold? Need I warm the mold before pouring in the hot caramel? Thank you.

European "Pyrex" glass is borosilicate - in USA that changed in the last couple years where "Pyrex" is a brand but now made of plain old window glass. any newerish stuff from USA is very likely to break.

I would warm the pan - working right up through boiling water temps before pouring melted sugar into the glass mold/pan.